How long do they last?
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Comments posted to this topic are about the item How long do they last?
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Very interesting & unique question, thanx!
Thanks & Best Regards,
Hany Helmy
SQL Server Database Consultant -
Thanks for this one! Got it wrong and learned something quite useful.
Just because you're right doesn't mean everybody else is wrong. -
Great Question Carlo, thanks!
Igor Micev,My blog: www.igormicev.com
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Great question, something new and quite useful.
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AP -
This was removed by the editor as SPAM
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Excellent illustration of how query folding and constant evaluation is used by the query optimizer. Many thanks Carlo.
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One of the most interesting questions I've seen. Thanks for that!
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Great question & thanks for the links.
Found this interesting in the Non-Foldable list on the MSDN page:
Expressions whose results depend on a local variable or parameter
Which casts a whole new light on parameter sniffing & why converting to local variables can help get around bad sniffs.
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Graham_Day (4/23/2015)
Excellent illustration of how query folding and constant evaluation is used by the query optimizer. Many thanks Carlo.+1
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Agreed. That was a great question. It perfectly illustrates how subtle differences in calling a function can have a huge impact on performance. Of course, it all goes back to understanding how things work and testing. Thanks for a really good question.
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Excellent question. I got it right by deduction more than understanding. I figured the scalar would run for each row but I would have thought the itvf would too...but then figured it wouldn't even be a question if the time was the same.
Good way to start the day by learning something new._______________________________________________________________
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Sean Lange (4/23/2015)
Excellent question. I got it right by deduction more than understanding. I figured the scalar would run for each row but I would have thought the itvf would too...but then figured it wouldn't even be a question if the time was the same. Good way to start the day by learning something new.I started from the opposite end, the itvf (because that's a part of the SQL world that I understand) and it was obvious it would only run once. Then I made the silly guess that the scalar valued function would be treated the same way, so I got it wrong.
Tom
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Great question, thanks.
Need an answer? No, you need a question
My blog at https://sqlkover.com.
MCSE Business Intelligence - Microsoft Data Platform MVP -
Great question, thanks.
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